Bonding of textile yarns to rubber



Patented June 13, 1950 UNITED STATES PATENT OFFICE BONDING OF TEXTILEYARNS T RUBBER Donald Entwistle, Coventry, England, asslgnor toCourtaulds Limited, London, England, a British company No Drawing.Application November 18, 1948, Serial No. 60,841. In Great BritainDecember This invention relates to the bonding of textile yarns torubber, for example, the bonding of duction, rayon cords often cannot beused in simple substitution for cotton cords owing to the lower degreeof bonding obtained. In order to improve the adhesion between rayoncords and rubber, many proposals have been made to treat the rayon yarnsor cords with specified adhesives. The adhesives hitherto employed havegenerally been of a resinous character but these are not whollysatisfactory as individual resins have limitations in certaindirections; for example, in some cases the resin in or on the rayonyarns may cause difliculties in the handling of the yarns preparatory tothe production of tires.

The object of the present invention is to pro-- vide an improved processfor bonding textile yarns to rubber.

According to the present invention, a process for the production of acomposite article comprising vulcanised rubber bonded to textile yarnsincludes the step of vulcanising rubber in contact with yarns which havebeen impregnated with a compound of a metal the sulphide of which isinsoluble in water.

Suitable metals are zinc, cadmium, mercury, copper, nickel and iron,preferred compounds of these metals are the hydroxides, carbonates andacetates. The metallic compounds may be applied to the yarns, or to suchwarns twisted into cords as an aqueous suspension or solution. Thus incases where a water-soluble compound such as cadmium acetate is to beused, it is suilicient to pass the 'yarn through an aqueous solution ofthe compound to obtain the desired impregnation. If a water-insolublecompound is to be used, for example zinc hydroxide or zinc carbonate,the yarn may be impregnated with a dispersion of the compound,preferably freshly-precipitated. In an alternative procedure awaterinsoluble compound may be deposited in situ in the yarns by passingthe yarns first through an aqueous solution of a metal compound such asthe sulphate and then through a bath of a compound such as sodiumcarbonate, which reacts with the water-soluble metal compound toprecipitate the desired metallic compound in the yarn.

A suitable proportion of the metallic compound is from 0.1 to 5 percent, preferably from 0.5 to 1 per cent of the weight of the yarn.

4 Claims. (Cl. 154-136) 2 When salts of strong acids such as sulphuricacid, nitric acid and hydrochloric acid are employed in the processaccording to the invention, an improved adhesion is obtained but at thesame time, the physical properties of the yarn, particularly the tensilestrength, are generally adversely afiected, presumably as a result ofthe acid condition prevailing during the vulcanisation.

It is therefore preferred to employ either a hydroxide or a metal saltof a weak acid such as carbonic acid or acetic acid since onvulcanising, according to the invention, with these compounds, little orno deterioration in the physical properties of the yarn is obtained.

The invention is particularly applicable to viscose rayon yarns but canbe applied to other rayon yarns, for example, those of stretched andsaponified cellulose acetate. It is also applicable to articles such asconveyor belting and V driving-belts. It is also applicable to tires andsimilar articles made from synthetic as well as natural rubber products,such as for example, the synthetic rubbers obtained by polymerisingbutadiene with other polymerisaible compounds such as styrene oracrylonitrile.

The process of the invention is of particular advantage in view of thehigh increase in the strength of the bond; another important advantageis that it enables the yarn to be treated before it is made into cordsand also simplifies the handling of the yarn.

It is believed that during the vulcanising operation in accordance withthe invention, the metallic compound in the yarn is converted into thesulphide by reaction with sulphur present in the rubber.

The invention is illustrated by the following examples, in which thepercentages are by weight.

Example 1 Viscose rayon tire yarn was passed through a l per centaqueous zinc sulphate solution, hydroextracted, passed through a 0.2 percent aqueous sodium carbonate solution to form zinc carbonate in situ inthe yarn, hydroextracted once more, dried and then used for theconstruction of tire cords. The dried yam contained about 0.65 per centof zinc carbonate.

The adhesion to rubber of these cords was found to be equal to theadhesion of a. similar untreated cotton cord and twice the adhesion of acord prepared from untreated viscose rayon so when tested as follows:

A number of 10 inch lengths of each type of cord are laid lengthwise onthe surface of a slab of an unvulcanised rubber composition measuring 10inches by 3 inches by M; inch and gently pressed by hand into therubber. The composition of the rubber stock is as 'follows, the partsbeing by weight:

Smoke sheets 100 parts. zinc oxide 40 parts, sulphur 3.5 parts, pine tar1 part, stearic acid 2 parts, antioxidant (phenyl beta-naphthylamine)1.5 parts and accelerator (mercaptobenzthiazole) 0.5 part.

The surface with the cords therein is now covered by a sheet ofregenerated cellulose while the other surface is covered with a canvassheet which is in turn covered by a sheet of regenerated cellulose. Thewhole assembly is now placed in a platen press and vulcanised at 30 lb.per square inch steam pressure for 60 minutes. The rubber slab isremoved from the press and the sheets of regenerated cellulose strippedoff giving a rubber slab having the cords buried therein with the uppersurfaces flush with the surface of the rubber. The canvas backing servesto render the slab inextensible while carrying out the adhesion tests.One end of each cord is now stripped out for about one inch and pulledin a direction along the surface of the rubber. the cord being bent backthrough an angle of 180 during the test. The pull required to separatethe rubber and the cord is determined.

An adhesion of a similar order was obtained by using a yarn obtained bypassing viscose rayon tire yarn through a dispersion offreshly-precipitated zinc hydroxide, hydroextracting and drying.

Example 2 Example 1 was repeated but with -the single exception that a 1per cent aqueous nickel sulphate solution was used in place of the zincsulphate bath.

The adhesion to rubber of the cords obtained was of the same order asthat obtained with the cords produced in Example 1.

Example 3 4 Example 4 viscose rayon tire yarn was passed through a 1 percent aqueous cadmium acetate solution, hydroextracted, dried and usedfor the construction of tire cords. The cords contained approximately 1per cent of cadmium acetate.

The adhesion to rubber of the cords obtained when tested as described inExample 1 was greater than that of the untreated yarn but was slightlyinferior to the adhesion obtained with the yarns obtained in Examples 1to 3.

What I claim is:

1. A process for the production of a composite article comprisingvulcanized rubber bonded to yarns of regenerated cellulose whichincludes the steps of impregnating the said yarn with a compound chosenfrom the group consisting of the hydroxides, carbonates and acetates ofa metal chosen from the group consisting of zinc, cadmium, mercury andnickel, placing the impregnated yarns in contact with unvulcanizedrubber and then vulcanizing the rubber so that the yarns are bonded tothe vulcanized rubber.

2. A process as claimed in claim 1 wherein the proportion of thecompound is from 0.5 to about 1.0 per cent by weight of the yarn.

3. A process for the production of a composite article comprisingvulcanized rubber bonded to yarns of regenerated cellulose whichincludes the steps of impregnating the said yarns with an aqueoussolution of a water-soluble compound of a metal chosen from the groupconsisting of zinc, cadmium, mercury and nickel, treating theimpregnated yarns with an aqueous solution of a water-soluble carbonatewhereby the carbonate of the said metal is deposited in situ in theyarns, placing the impregnated yarns in contact with unvulcanized rubberand then vulcanizing the rubber so that the yarns are bonded to thevulcanized rubber.

4. A process as claimed in claim 3 wherein the proportion of compound isfrom about 0.5 to about 1.0 per cent by weight of yarn.

DONALD ENTWISTLE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,184,015 Price May 23, 19161,723,581 Ruderman Aug. 6, 1929 2,054,780 Bley Sept. 15, 1936 2,314,976Gazdik Mar. 30, 1943

1. A PROCESS FOR THE PRODUCTION OF A COMPOSITE ARTICLE COMPRISINGVULCANIZED RUBBER BONDED TO YARNS OF REGENERATED CELLULOSE WHICHINCLUDES THE STEPS OF IMPREGNATING THE SAID YARN WITH A COMPOUND CHOSENFROM THE GROUP CONSISTING OF THE HYDROXIDES, CARBONATES AND ACETATES OFA METAL CHOSEN FROM THE GROUP CONSISTING OF ZINC, CADMIUM, MERCURY ANDNICKEL, PLACING THE IMPREGNATED YARNS IN CONTACT WITH UNVULCANIZEDRUBBER AND THEN VULCANIZING THE RUBBER SO THAT THE YARNS ARE BONDED TOTHE VULCANIZED RUBBER.